Thread controlling mechanism for sewing machines



n4. oaWING MACHiNES.

Search Room Jan. 9, 1940.

THREAD M. MCCANN 2,186,762

CONTROLLING MECHANISM FOR SEWING MACHINES Filed Feb. 9, 1938 3Sheets-Sheet 2 awucwto'a (1 tram;

Search Room Jan. 9, 1940. M. MCCANN 2,186,762

THREAD CONTROLLING MECHANISM FOR SEWING MACHINES Filed Feb. 9, 1938 3SheetsSheet 3 Patented Jan. 9, 1940 UNITED STATES PATENT OFFICE THREADCONTROLLING MECHANISM FOR SEWING MACHINES Application February 9, 1938,Serial No. 189,503

14 Claims.

This invention relates to sewing machines more particularly of thesingle-thread chain-stitch type adapted for the sewing of buttons togarments.

The single-thread chain-stitch button-sewing machine, as commonlyconstructed, is fitted with a needle-bar-vibrating cam cut so that theneedle makes its last two or three complete reciprocations through thesame thread-hole in the button without making any lateral movement andthus causes the usual final knot-tying stitches to be formed. When theneedle descends successively through the same thread-hole in the button,a portion of the needle-thread is doubled back upon itself, and as theneedle continues to descend this doubled portion of the thread is drawninto the work and held in such position by friction only until theadvancing beak of the looper enters the subsequently formed thread-loopcast out by the needle as it begins to ascend, the doubled portion ofthe thread then being drawn down out of the work by the action of thetake-up in setting the stitch. In practice, it has been found that whensewing buttons on a comparatively heavy material, such as that used inthe making of overcoats and the like, skipping of stitches frequentlyoccurs during the formation of the knot-tying stitches at the end of thebutton-sewing operation, resulting in a tack which may easily beraveled. It has been discovered that this skipping of the stitches iscaused by the reeving of the thread through the eye of the needle as thelatter descends causing only a very small portion of the needle-threadto be doubled back upon itself, and as a result this comparatively shortlength of doubled thread, instead of being held in the work, is drawndown out of the work before the needle reaches the bottom of its stroke.When this occurs, the thread-loop formed as the needle begins itsupstroke is uncontrolled and, due to the tension on the needle-threadand the position of the previously formed stitches, is frequently drawnrearwardly of the needle, in which position it is practically impossiblefor the advancing beak of the looper to invariably seize theneedle-thread loop. Obviously, when the needle-thread loop is not seizedby the looper, no knot-tying stitch is formed and the resultingbutton-securing tack may, of course, be easily raveled. This fault isaccentuated by the excessive straining of the needle-thread between thenipper and the preceding stitch in the work, since this straining of thethread tends also to prematurely reduce the needle-thread loop as theneedle begins its upstroke and before the looper reaches itsloop-seizing position. These conditions have existed in the past and areextremely troublesome in that much of the work done by machines ashereinbefore constructed is defective. 5

It is the primary object of the present invention to provide athread-controlling mechanism designed to draw through the eye of theneedle a length of thread for the purpose of preventing the skipping ofstitches during the 10 formation of the knot-tying stitches at the endof a button-sewing operation. Stated in other words, the object of thepresent invention is the provision of means automatically operableduring the formation of the knot-tying stitches at 5 the end of thesewing operation for producing a bight in the needle-thread between theneedle-eye and the work-support, thereby to prevent the skipping ofstitches.

With the above and other objects in view, as will hereinafter appear,the invention comprises the devices, combinations, and arrangements ofparts hereinafter set forth and illustrated in the accompanying drawingsof a preferred embodiment of the invention, from which the severalfeatures of the invention and the advantages attained thereby will bereadily understood by those skilled in the art.

In the accompanying drawings, Fig. l is a side elevation of abutton-sewing machine embodying the invention.

Fig. 2 is a front elevation of the sewing machine, showing thethread-controlling mechanism in retracted or ineffective position.

Fig. 3 is an enlarged perspective view of my improved thread-controllingmechanism, showing, in full lines, the thread-engaging element inretracted or ineffective position and, in dotted lines, in position inwhich maximum slack occurs.

Fig. 4 is a transverse sectional view through the work-clamp at thesewing point, showing the thread-engaging finger of thethread-controlling mechanism just as it engages the needlethreadpreparatory to pulling a length of thread through the needle-eye.

Fig. 5 is a view similar to Fig. 4, showing the thread-engaging fingerin position in which maximum thread-drawing occurs.

Fig. 6 is a longitudinal sectional view through the work-clamp at thestitching point, illustrating the manner in which the needle, during thenormal sewing operation, forms a loop in the needle-thread for entranceby the beak of the looper.

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Figs. 7 and 8 are longitudinal sectional views through the work-clamp atthe stitching point of a machine not fitted with the present improvementat the respective times when the needlethread loop is correctly formedfor entrance by the looper to'form the knot-tying stitch and when it isincorrectly formed, causing skipping of the stitch.

Fig. 9 is an enlarged front elevation of a portion of Fig. 8, partly insection, showing the way in which the needle-thread loop is incorrectlypositioned rearwardly of the needle.

Fig. 10 is a longitudinal sectional view similar to Fig. 7 of a machinefitted with my improved thread-controlling mechanism, illustrating themanner in which the needle-thread loop invariably is correctly formedfor entrance by the looper.

Referring to the drawings, the machine is constructed with a frameincluding a bed I from which rises a standard 2 of the overhangingbracket-arm 3 terminating in a head 4. The bed I includes an extension Iof reduced width which constitutes a work-supporting arm.

The stitch-forming mechanism 15 constructed substantially in accordancewith the disclosures in the U. S. patents to H. W. Morris, No.1,606,173, and M. McCann, No. 1,941,481, dated Nov. 9, 1926 and Jan. 2,1934, respectively, and comprises an endwise reciprocatory and laterallyvibratory needle 5, rotary non-threaded looper 6, and looppositioner andneedle-guide 6, all of which are actuated in the regular manner. Theneedle 5 is secured to the usual needle-bar I which is given its endwisereciprocatory movements by means of the link-connection 8 with thevibratory arm 9 fixed to the rock-shaft l0 actuated by thepitman-connection II from the eccentric l2 on the main-shaft I3.

The needle-bar is guided in its reciprocatory movements by upper andlower bearing blocks l4 and IS. The upper bearing block I4 is fixed to apivot-stud [6 which is journaled in the head 4. The lower bearing blockI5 is fixed to a pivotstud I! which is carried by theneedle-bar-vibrating lever l8 fulcrumed on the adjustable block l9 andcarrying a follower 20 entering the camgroove 2| in theneedle-bar-vibrating cam 22 mounted on the upper end of the verticalfeedshaft 23. The feed-shaft 23 makes only one complete rotation percomplete button-sewing period and is driven by the worm-and-gearconnection 24 with the main-shaft l3.

The work-holding means and the mechanism for imparting the requiredmovement thereto are of common form, and are constructed substantiallyin accordance with the disclosure in the U. S. patent to M. McCann, No.1,998,587, dated Apr. 23, 1935. The work-holder essentially comprises anarm 25 pivoted at 26 upon a carriage 21 mounted for endwise movement insuitable ways 28 on the bed I. Attached to the forward end of the arm 25are two late: ally separable buttonengaging jaws 29 which grip thebutton and correctly position it relative to the reciprocatory needle 5.As clearly illustrated in Figs. 1 and 2, the work-holder is fitted witha button-spacing member 30 which is identical in construction with thatdisclosed in the above mentioned U. S. Patent No. 1,998,587.

As hereinbefore stated, the primary object of the present invention isthe provision of a novel thread-controlling mechanism which improves thesewing characteristics of the machine. This mechanism preferablycomprises an oscillatory thread-engaging finger 3 I, the upper end ofwhich is clamped upon one end of a rock-shaft 32 journaled in hearingsin the brackets 33 and 34. The bracket 33 is secured to the head 4 bythe screws 35, while the bracket 3d is secured to the standard 2 by thescrews 36. The rearward end portion of the rock-shaft 32 is preferablybent to the left of its axis of movement to provide, in effect, arock-arm, designated as 31. Mounted upon the rock-arm 31 is acam-follower 38 which is secured in correct position by the set-screw39. The camfollower is preferably adjustably secured upon the rock-armin order that the proper timing of the thread-controlling mechanism maybe effected.

As will be observed from Figs. 1 and 3, the cam-follower 38 is normallyheld in contact with the under surface of the needle-bar-vibrating cam22 by the spring 40 which acts between the rock-arm 3'! and the standard2. In order to impart an oscillatory movement to the thread-wipingfinger 3|, thereby to move it across the needle-path, theneedle-bar-vibrating cam 22 has secured thereto upon its under surface,preferably by screws 4I, a suitably formed cam-lobe 42 which engages thecam-follower 38 and positively moves it into the dotted line positionshown in Fig. 3. The effective surfaces of the camlobe and thecam-follower are preferably designed so that the thread-controllingaction occurs during the last stitch-forming cycle only or, in otherwords, during the time in which the knot-tying stitches are beingformed. As will be seen in Fig. 4, the thread-engaging finger is movedinto position to just engage the needle-thread T as the needle 5 startsits descending movement or, in other words, as the final or knot-tyingstitch-forming cycle begins. As the needle continues to descend andbefore it enters the threadhole in the button B (see Fig. 5), the threadengaging finger moves across the needle-path and draws through the eyeof the needle a short length of thread given up by the usual take-up.When the needle enters the thread-hole in the button B, the thread Tsimply slips off the free end of the thread-engaging finger, whichcontinues to move until it reaches its extreme righthand position. Thethread-engaging finger remains in this position until the completion ofthe knot-tying stitch-forming cycle, after which it is returned to itsinelfective position by the spring 40, (Fig. 2).

Following is a more detailed description of the operation of my improvedthread-controlling mechanism. Referring to Fig. 6, it will be seen thatduring the normal button-sewing operation the laterally vibrating needle5, as it starts to ascend, forms a thread-loop T below theworksupporting arm I, about which the previously formed thread-loop Tengaged by the looper 6 will be subsequently cast. Since the laterallyvibrating needle 5 alternately penetrates different thread-holes in thebutton B, during the normal sewing operation, practically no skipping ofstitches occurs. However, when the needle repeatedly penetrates the samethread-hole in the button, as it does when forming the knot-tyingstitches, the thread T is doubled upon itself at T (see Fig. 7), andthis doubled portion of the thread T is held in the work by frictiononly. If the thread T reeves through the eye of the needle as the latterdescends, the folded portion of the thread T is relatively short and islikely to be drawn down out of the work by the needle before the latterreaches the lowermost point;

of its stroke, as shown in Fig. 8. When this occurs the thread-loop Tinstead of being correctly formed transversely of the needle, asillustrated in Figs. '7 and 10, is frequently formed rearwardly of theneedle, see Figs. 8 and 9, because of the fact that one limb of thethread-loop T extends from the previously formed stitches S in the workwhich are disposed rearwardly of the needle 5. Obviously, when thethread-loop T is formed rearwardly of the needle instead of transverselythereof, the advancing beak of the looper does not seize it and,consequently, no knot-tying stitch is produced. This defect has beenlargely overcome by employing a threadcontrolling mechanism which,during the knottying stitch-forming cycle, draws through the needle-eyea short length of thread which is being given up by the take-up, therebyincreasing the amount of thread T between the needle-eye and thepreceding stitch in the work. This increased amount of thread permitsthe formation by the needle 5 of a longer doubled thread-portion T seeFig. 10. The primary advantage of this longer thread-portion is that afold is provided having an amount of thread in excess of that requiredby the needle as it descends through the work during the finalstitch-forming cycle. Since the doubled thread-portion T is notcompletely drawn out of the work, the thread of the needle-loop T isconstantly under control, inasmuch as one limb thereof is maintained incontact with the blade of the needle 5 and the loop T is formedtransversely of the needle, in which position it is unerringly seized bythe looper 6.

While in accordance with the provisions of the statute, I haveillustrated and described my invention as applied to a button-sewingmachine adapted for attaching four-hole buttons with a stay-button B toa body-fabric W by two parallel groups of stitches, it is to beunderstood that my improvement will function equally well on any othercommon type of button-sewing or tacking-and-barring machine.Furthermore, the invention is not to be understood as limited to thedetails of construction and relative arrangement of parts shown anddescribed, as such details and relative arrangements may obviously bevariously modified by those skilled in the art within the spirit of theinvention.

Having thus set forth the nature of the invention, what I claim hereinis:

1. In a sewing machine adapted to sew a predetermined number of stitchesand then come to rest, the combination with a work-support andstitch-forming instrumentalities including a reciprocatory needleadapted to be vibrated during a portion of the stitching operation andoperated in a fixed path during another portion of the stitchingoperation, of means located above the work-support and operable toproduce a bight in the needle-thread to insure proper stitch-formationduring that portion of the sewing operation in which the needle operatesin a fixed path.

2. In a sewing machine adapted to perform a definite sewing operation,the combination with stitch-forming instrumentalities including areciprocatory needle adapted to be vibrated during a portion of thesewing operation and operated in a fixed path during another portion ofthe sewing operation, of means operable only during the time in whichthe needle is operating in a fixed path to produce a bight in the threadto prevent the skipping of stitches.

3. A sewing machine adapted to sew a predetermined number of stitchesand then come to rest, having, in combination, work-holding means,stitch-forming instrumentalities including a threaded reciprocatoryneedle, means for efiecting relative lateral movement between saidwork-holding means and said needle during a number of said predeterminedstitches and for holding said work-holding means and said needle againstrelative lateral movement during other of said predetermined stitches,and means constructed and. arranged to form a bight in the needle-threadabove said work-holding means to facilitate proper stitch-formationduring that portion of the sewing operation in which there is norelative lateral movement between the work-holding means and the needle.

4. In a sewing machine, adapted to perform a definite sewing operationand then come to rest, work-holding means, stitch-forming mechanismincluding a threaded reciprocatory needle, means for effecting relativelateral movement between said work-holding means and said needle duringa portion of said sewing operation and for holding said work-holdingmeans and said needle against relative lateral movement during anotherportion of said sewing operation, and means operable only during thetime in which there is no relative lateral movement between the workholding means and the needle for producing a bight in the needle-threadabove said work-holding means to insure proper stitch-formation in thatportion of the sewing operation.

5. A sewing machine adapted to sew a predetermined number of stitchesand then come to rest, having, in combination, work-holding means,stitch-forming mechanism including a threaded eye-pointed reciprocatoryneedle and a cooperating loop-taker, means for efiecting relativelateral movement between said work-holding means and said needle duringa number of said predetermined stitches and for holding saidwork-holding means and said needle against relative lateral movementduring other of said predetermined stitches, and means automaticallyoperated by said last-named means for drawing a length of thread throughthe eye of the needle.

6. In a sewing machine, the combination with work-holding means andstitch-forming instrumentalities including a reciprocatory needle, ofmeans operable only during predetermined stitch-forming cycles toproduce slack in the thread above the work-holding means to prevent theskipping of stitches during said predetermined stitch-forming cycles.

'7. A sewing machine having, in combination, work-holding means,stitch-forming mechanism including a reciprocatory needle and acooperating loop-taker, means including a cam for controlling thedistribution of the stitches in the work, and means operated by said camfor forming a bight in the thread.

8. A sewing machine having, in combination, work-holding means,stitch-forming mechanism including a threaded eye-pointed reciprocatoryneedle and a cooperating loop-taker, means including a cam forcontrolling the distribution of the stitches in the work, and meansactuated by said cam for forming a bight in the thread, said last-namedmeans including a thread-engaging finger, a shaft supporting saidfinger, and means carried by said shaft and engaging said cam.

9. In a sewing machine the combination with work-holding means andstitch-forming mechanism including an eye-pointed reciprocatory needle,of a thread-controlling mechanism comprising a thread-engaging finger, ashaft sup- UUlll porting said finger, and means for periodicallyactuating said shaft thereby to cause said threadengaging finger to drawthrough the needle-eye a length of thread.

10. In a sewing machine the combination with work-holding means andstitch-forming mechanism, of a threadcontrolling mechanism comprising athread-engaging finger, a shaft supporting said finger, positive meansfor imparting movement to said thread-engaging finger in one direction,and impositive means for imparting movement to said thread-engagingfinger in the opposite direction.

11. A sewing machine, adapted to perform a definite sewing operation andthen come to rest, comprising a frame including a work-support and anoverhanging arm, work-holding means, stitch-forming instrumentalitiesincluding a threaded eye-pointed reciprocatory needle, and meansconstructed, arranged and timed to engage the needle-thread above thework-support to draw through the eye of the needle before saidstitch-forming instrumentalities complete said sewing operation a lengthof thread to be used in said sewing operation.

12. In a sewing machine, the combination with a work-support andstitch-forming instrumentalities including a threaded reciprocatoryneedle and a cooperating loop-taker, of means for repeatedlyreciprocating said needle through the same needle aperture therebyforming in the work a doubled portion of thread, and means operable toinsure that the length of thread comprising the doubled portion is ofsufiicient length to prevent said doubled portion from being prematurelypulled out of the work during stitch-formation.

13. In a sewing machine, the combination with a work-support andstitch-forming instrumentalities including a threaded reciprocatoryneedle and a cooperating loop-taker, of means for repeatedlyreciprocating said needle through the same needle aperture therebyforming in the work a doubled portion of thread, and means located abovethe work-support and operable to increase the length of thread formingthe doubled portion so that the latter will not be prematurely pulledout of the work during stitch-formation.

14. In a sewing machine, the combination with a work-support andstitch-forming instrumentalities including a threaded reciprocatoryneedle and a cooperating loop-taker, of means for reciprocating saidneedle a plurality of times through the same needle aperture therebyforming in the work a doubled portion of thread, and means including afinger adapted to engage the thread between the work-support and theneedle when the latter is out of the work to increase the length ofthread forming the doubled portion so that said doubled portion will notbe prematurely pulled out of the work during stitchformation.

MICHAEL McCANN.

